Hi guys. My boot time is pretty long(14.2 secs) for my system and I think this is because im using CSM instead of UEFI. But when I switch to uefi my system gaves me a gop error. I'm using Asus ROG Strix RX 580 OC(8 GB). I updated my rom with GOPupd and flashed it. But it didn't help. What can I do?
My system:
CPU: AMD Ryzen 7 2700x
Drive: XPG SX8200 PRO M2
MOBO: MSI B450M GAMING PLUS
GPU: ASUS ROG STRIX RX 580 OC (8 GB)
RAM: CORSAIR VENGEANCE LPX 16 GB 3000 MHZ (1X16)

Here is my rom dump from GPU-Z:
https://ufile.io/4u6o2adw

UPDATE: Found official amd gop drivers. But there are two seperate versions for pre-SOC15 and post-SOC15. My device id is 1002 - 67DF. And here are the pre-soc15 id ranges:

(0x6880, 0x689f), (0x68A0, 0x68Bf), (0x68C0, 0x68Df), (0x68E0, 0x68FF), (0x9640, 0x964f), (0x9800, 0x980f), (0x9990, 0x99Af), (0x6700, 0x671f), (0x6720, 0x673f), (0x6740, 0x675f), (0x6840, 0x685f), (0x6760, 0x677f), (0x6780, 0x679f),  (0x6800, 0x681f),  (0x6820, 0x683f), (0x6600, 0x663f), (0x6660, 0x667f), (0x1304, 0x131d), (0x6640, 0x665f), (0x67a0, 0x67bf), (0x9830, 0x983f), (0x98b0, 0x98bf), (0x6900, 0x691f), (0x6920, 0x693f), (0x6960, 0x697f), (0x7300, 0x7304), (0x67C0, 0x67DF), (0x67E0, 0x67Ff), (0x6980, 0x699f), (0x6940, 0x695f), (0x9850, 0x985f), (0x9870, 0x988f), (0x98e0, 0x98ff), (0x9890, 0x98af), (0x98c0, 0x98df)
 

0x67DF is in the list. So I think I should move on with pre-SOC15 driver. I downloaded it. And it's a 1 mb .efi file. Now I don't know how to use it or how to inject it to my vbios or something. Any helps?

CSM/legacy vs UEFI does not really matter in boot times, especially not in a length like you mention. Test clean OS install, what is time then?
When you updated vBIOS via GOPUPD tool, could you then boot with CSM disabled?